Aren't the vast majority of market participants already operating outside the blockchain, relying on exchanges and sometimes on so-called "L2" networks like Lightning? I think the majority of Bitcoin and Ethereum proponents are already talking about them as "digital gold" instead of digital currency. The mining pools have also blocked any attempt to make the Bitcoin blockchain more efficient at transactions (by keeping the block size small), so on-chain trading is doomed to remain an extremely low-rate event for the foreseeable future. Is it still at 7-10 transactions/second globally?

So overall it seems quite easy to force the matter and implement KYC and AML for msot legal Bitcoin transactions.